OPC Data Access 2.05 & 3.0 Client
OPC Data Access 2.05 & 3.0 Client Communication Protocol
Supported device types and versions of devices
Communication line configuration
Communication station configuration
I/O tag configuration
Browsing of the OPC server address space
Historical Data Access
Tell commands
DCOM configuration for connecting a remote OPC server
Errors and problems
Literature
Changes and modifications
Document revisions
Supported device types and versions
The protocol supports the client side of a communication with OPC (OLE for Process Control) DA (Data Access) servers according to the OPC DA specification ver. 2.05A and 3.0. It also supports the client side of communication with OPC HDA (Historical Data Access) servers according to OPC HDA specifications ver. 1.20.
Communication line configuration
Communication line category: OPC.
OPC parameters:
OPC Host: Only Remote entrance requires it. Computer, where the program D2000 OPC Server is installed in - it is defined for OPC server type "Remote" only (maximum string: 50 characters). You can define names according to the UNC convention (e.g. \\server or server), DNS domain names (e.g. domain.com, example.company.com) or IP address (196.54.23.113).
Backup Host: Only Remote entrance requires it. It is backup OPC host. If the parameter is defined, after the communication has failed, the process D2000 KOM is attempting to establish connection alternately with the OPC host and Backup host.
OPC Server: Name (ProgID) of the OPC server (maximum string: 50 characters).
Server Type: according to the server type – InProc, Local or Remote.
Communication line parameters
Following communication line parameters can be configured for protocol "OPC Data Access 2.05 & 3.0":
Tab. No. 1
Name | Description | Unit | Default value |
|---|---|---|---|
OPC HDA: Server if Available | OPC HDA server name (ProgID), if it is available. OPC HDA functions not to be activate use empty text. | - |
|
OPC HDA: Max. Number of Values | Sets the parameter NumItems at synchronous reading of historical "raw" values. The implicit value 0 (zero) means all values in the given interval. | - | 0 |
Sequenced Transactions | Starts the sequencing of calling the function Refresh2 of interfaces Async I/O 2.0 and Async I/O 3.0. The calling executes after the first calling has been finished (after it gets the values). | YES/NO | NO |
Repeat Failed Group Activation | Failed OPC group activations will be attempted again after a delay specified by parameter "Group reactivation delay". | YES/NO | YES |
Group Reactivation Delay | A delay after which a failed OPC group activations is repeated if repetition is enabled by parameter "Repeat failed group activation". | sec | 30 |
Reconnect After Failed Group Activation | When an OPC group activation fails, KOM disconnects from OPC server and reestablishes a connection. Parameter is relevant in a configuration of redundant OPC servers (after a disconnect from an OPC server follows a reconnect to alternate OPC server where group activation may be successful). | YES/NO | NO |
GetGroupState Period | Period of executing the call of GetGroupState of interface IOPCGroupStateMgt. This synchronous call is repeated periodically and detects the problems which could occur in communication with OPC Server. | sec | 10 |
Accept All GetGroupState Errors | All the errors returned by calling of "GetGroupState" of interface IOPCGroupStateMgt are considered to be fatal (they will result in disconnect from the OPC server and reconnect or in restart of the KOM process). An example of error message returned by "GetGroupState": | YES/NO | NO |
Stop KOM When OPC Server Fails | Allows to stop KOM process when the fatal error occurs in communication. See the Note. | YES/NO | NO |
Disconnect On Passive | Only the active KOM process (i.e., the active instance connected to the HOT server) communicates with the OPC server. The KOM process, which becomes passive (by changing the active instance or switching the redundancy), closes the connection to the OPC server. | YES/NO | NO |
Note:
Fatal abort of communication with OPC Server causes the COM/OPC errors at callings:
GetGroupState of interface IOPCGroupStateMgt,
"Write" of interface IOPCASyncIO2, IOPCASyncIO3 and IOPCSyncIO2,
"Read" of interface IOPCASyncIO2, IOPCASyncIO3 and IOPCSyncIO2.
Communication station configuration
Communication protocol: OPC Data Access 2.05 & 3.0.
Station address requires:
OPC Group Name - maximum string: 80 characters. This name is only formal in most cases and has no direct relation to the address scheme of devices communicating with the OPC server. The name of group must be unique, two stations cannot the same OPC Group Name within one link.
Type - data access type. You can chose one of the Async I/O 2.0, Async I/O 3.0 and Synchronous I/O options. The Async I/O 2.0 option - the asynchronous OPC interfaces IOPCAsyncIO2 and IOPCDataCallback (OnDataChange and OnReadcompleted call-back procedures) are used for data reading. The Synchronous I/O 2.0 option - OPC interface IOPCSyncIO is used. The Async I/O 3.0 option - OPC interfaces IOPCAsyncIO3 and IOPCDataCallback (OnDataChange and OnReadCompleted call-back procedures) are used for value reading of OPC items
Create Active - if the option is checked, the OPC group is active and OPC items in this group get values. If the option is not checked, the OPC group and items are initialized, but the OPC items do not get values. It is possible to block the OPC group - station temporarily. The option controls the pActive parameter of SetState call of the OPC interface IOPCGroupStateMgt.
Update Rate - it is given in milliseconds and defines the maximum speed of OPC item value changes for the option Async I/O 2.0 or Async I/O 3.0. It is transferred as parameter pRequestedUpdateRate of SetState call of OPC interface IOPCGroupStateMgt. Warning - the information, set in tab Time parameters in dialog window Communication station - configuration dialog box defines the read rate of OPC items.
% Deadband - the parameter range is from 0.0 up to 100.0%. The parameter can be only used for analog type of items and determines the minimal change of the item for sending the value from the server to clients. For calculation, the OPC server uses the range defined by parameters High EU and Low EU, which can be get by using the interface IOPCItemProperties. Default value of this parameter is 0.0. Value of % Deadband is transferred by means of parameter pPercentDeadband of the SetState call of the OPC interface IOPCGroupStateMgt.
Note: The protocol OPC Client described in this topic does not support the OPC interface IOPCItemProperties. For further information read up the document listed in the section Literature.Time Bias - If OPC server and OPC client do not run in the same time zone, the parameter (given in minutes) will be used for the correct calculation of the value time of the OPC item - time stamp. Default value of the parameter is 0 (zero). For further information read up the documents listed in the section Literature.
Station protocol parameters
The following station protocol parameters can be defined:
Name | Description | Unit | Default value |
|---|---|---|---|
Do Read after Write | Allows to verify the value after the recording by synchronous reading. | YES/NO | NO |
Prefer Synchronous Write | Allows to write data into OPC Server only by synchronous interface IOPCSyncIO2. | YES/NO | NO |
Prefer VQT Write | Using the Async I/O 3 option allows to write data by WriteVQT function of IOPCASyncIO3 interface (i.e. the write that transfers the quality and the timestamp together with the value). | YES/NO | NO |
Full Debug | Activates the debug list. It increases the number of information about the communication operation. It is recommended to use only in detection of the problems and debugging. | YES/NO | NO |
Merz OPC Server Type | Special mode for communication with OPC Servers made by Merz company. The conversion to/from MS DOS Date Time Format (2 x WORD) is used for values of TiA and ToA type. | YES/NO | NO |
AddItems Delay | Delay which is artificial inserted between the AddItems callings to slow down the initialisation phase. | ss:mss | 0 |
QERR Value | Integer value of "ERROR" state for conversion into Qi - quaternary input. | 0,1,2,3 | 3 |
QOFF Value | Integer value of "OFF" state for conversion into Qi - quaternary input. | 0,1,2,3 | 2 |
QON Value | Integer value of "ON" state for conversion into Qi - quaternary input. | 0,1,2,3 | 1 |
QTRANS Value | Integer value of "TRANS" state for conversion into Qi - quaternary input. | 0,1,2,3 | 0 |
Keep Values Valid as Weak | If the quality of OPC item changes into "BAD", the value of I/O tag will be valid with Weak flag. | YES/NO | NO |
Don't Repeat Failed AddItems | Blocks the effort to call AddItems which still repeats after its failure. | YES/NO | NO |
Do AddItems in Single Call | Activates all the items of group by one calling. It can quicken the OPC communication start. | YES/NO | NO |
Transaction Timeout | Keeps files of all callings of Write and Refresh2 functions as separate transactions. If they do not end up (successful or unsuccessful) to this timeout, the error message will occur in trace file of communication. | sec | 120 |
Reconnect/Reinitialization Delay | Timeout, which delays the repeat of failed operation:
| sec | 5 |
Do Sync Read Before Write If Unk. Type | Enables a synchronous reading of the item value before the writing in case that KOM process do not know correct item data type (i.e. if there is an default value of data type "Empty/Default (VT_EMPTY)", the value must be written). | YES/NO | YES |
Status Item Name | Address of OPC Item (OPC Item ID), which contains the OPC server or OPC group error status (e.g. depending on the state of communication). An I/O tag with this address must also be configured. | - | - |
Status Item Inverted Operation | Interpretation of the OPC Item Status Item Name with error status of OPC server or OPC group. | YES/NO | NO |
Map NonSpecific as Flag | Mapping the OPC DA flag of quality Non Specific into the attributes of I/O tag value. | None, FA, FB, FC, FD, FE, FF, FG, FH, FI, FJ, FK, FL, FM, FN, FO, FP | None |
Map LocalOverride as Flag | Mapping the OPC DA flag of quality LocalOverride into the attributes of I/O tag value. | ||
Map ConfigError as Flag | Mapping the OPC DA flag of quality Config Error into the attributes of I/O tag value. | ||
Map NotConnected as Flag | Mapping the OPC DA flag of quality Not Connected into the attributes of I/O tag value. | ||
Map DeviceFailure as Flag | Mapping the OPC DA flag of quality Device Failure into the attributes of I/O tag value. | ||
Map SensorFailure as Flag | Mapping the OPC DA flag of quality Sensor Failure into the attributes of I/O tag value. | ||
Map LastKnown as Flag | Mapping the OPC DA flag of quality Last Known into the attributes of I/O tag value. | ||
Map CommFailure as Flag | Mapping the OPC DA flag of quality Comm Failure into the attributes of I/O tag value./td> | ||
Map OutOfService as Flag | Mapping the OPC DA flag of quality Out Of Service into the attributes of I/O tag value. | ||
Map WaitingForInitData as Flag | Mapping the OPC DA flag of quality Waiting For Initial Data into the attributes of I/O tag value. | ||
Map LastUsable as Flag | Mapping the OPC DA flag of quality Last Usable into the attributes of I/O tag value. | ||
Map SensorCal as Flag | Mapping the OPC DA flag of quality Sensor Cal into the attributes of I/O tag value. | ||
Map EGUExceeded as Flag | Mapping the OPC DA flag of quality EGU Exceeded into the attributes of I/O tag value. | ||
Map SubNormal as Flag | Mapping the OPC DA flag of quality Sub Normal into the attributes of I/O tag value. | ||
Reconnect After Error Count | If consecutive number of errors during reading equals to the value of this parameter, reinitialisation of OPC connection will be performed. Value of zero means that reinitialisaton will not be performed (default behaviour). Current implementation handles only errors in synchronous mode (type setting to "Synchronous I/O" in tab Address of Station object). | - | 0 |
I/O tag configuration
Possible I/O tag types: Ai, Ao, Ci, Co, Di, Qi, Dout, TiA, ToA, TiR, ToR, TxtI, TxtO.
I/O tag address requires to define OPC Item ID (maximum string: 200 characters). If OPC server supports interface IOPCBrowseServerAddressSpace, the address OPC Item ID may be selected directly from the address list supported by OPC server (it is needed to click on button "Browse Items...", see the section Browsing of OPC server address space.
Note: if I/O tag's address is specified as %IGNORE, such an I/O tag will be ignored.
Further required parameters (OPC Item Parameters) are:
Type - required data type VARIANT. Default value is Empty/Default (VT_EMPTY), - the OPC server makes a decision on the VARIANT type of the item.
Item Active - if the option is checked, the item will be active and get values from the server. The option is transferred by the parameter bActive of the pItemArray structure into the AddItems call of the OPC interface IOPCItemMgt.
Bit Index - bit number. It is defined as a number within the range of 0..31. It can be only used for the Di and Dout value types. Value received from the OPC server is being converted to 32 bit unsigned number and the binary value of the I/O tag is the value of particular Bit Index. The conversion is allowed only for the VARIANT values of integer types (e.g. VT_UI1, see the adjusted parameter Type).
Array Index - the option (a number within the range of 0..32767) determines the index in the array of received VARIANT value from the OPC server of the Array type. Array value on the defined position is assigned to the value of the I/O tag.
The protocol supports the configuration of tab Destination of I/O tag. If the value of OPC item is of Array type, the communication protocol copies the values of array from the item ArrayIndex into column of structured variable. The size of structured variable is taken into consideration. If the array VARIANT is smaller than number of structured variable rows the empty rows of structured variable will be invalid. If the number of structured variable rows is smaller than array VARIANT, the values which are remaining are ignored.
Browsing of the OPC server address space
Clicking on button "Browse Items..." in the Address tab of I/O tag dialog box opens another dialog window "OPC Item Browser".
Here the user can choose the items from the OPC server address space. The item representation can be "Hierarchical" or "Flat". Some of the OPC servers do not support the "Hierarchical" representation (the button "Hierarchical" is disabled). If both the representations are supported the "Hierarchical" may be switched over to "Flat" and vice-versa.
Hierarchical - enables browsing of the OPC server address space according to the logical hierarchical groups and subgroups. The dialog box "OPC Item Browser" is divided into two parts:
hierarchical tree structure (top part)